my_i2c.cpp

00001 #include "mbed.h"
00002 #include "my_i2c.h"
00003 
00004 DigitalInOut sda(p9);
00005 DigitalInOut scl(p10);
00006 
00007 
00008 #define SDA(state) if (state) { \
00009   sda.input ();                 \
00010   sda = 1;                      \
00011 } else {                        \
00012   sda = 0;                      \
00013   sda.output ();                \
00014 }
00015 
00016 #define SCL(state) if (state) { \
00017   scl.input ();                 \
00018   scl = 1;                      \
00019 } else {                        \
00020   scl = 0;                      \
00021   scl.output ();                \
00022 }
00023 
00024 #define IO_DELAY() wait_us (1)
00025 
00026 
00027 void my_i2cWriteByte (unsigned char byte);
00028 bool my_i2cGetAck ();
00029 unsigned char my_i2cReadByte ();
00030 
00031 
00032 bool
00033 my_i2cStart (unsigned char slaveAddress)
00034 {
00035   SDA(1);
00036   SCL(1);
00037   IO_DELAY();
00038   SDA(0);
00039   IO_DELAY();
00040 
00041   my_i2cWriteByte (slaveAddress);
00042 
00043   return my_i2cGetAck ();
00044 }
00045 
00046 
00047 bool
00048 my_i2cStop ()
00049 {
00050   SDA(0);
00051   SCL(0);
00052   IO_DELAY();
00053 
00054   SCL(1);
00055   IO_DELAY();
00056 
00057   SDA(1);
00058   IO_DELAY();
00059 
00060   return true;
00061 }
00062 
00063 
00064 bool
00065 my_i2cRepeatedStart (unsigned char slaveAddress)
00066 {
00067   SCL(0);
00068   IO_DELAY();
00069 
00070   SDA(1);
00071 
00072   IO_DELAY();
00073 
00074   SCL(1);
00075 
00076   IO_DELAY();
00077 
00078   SDA(0);
00079   my_i2cWriteByte (slaveAddress);
00080 
00081   return my_i2cGetAck ();
00082 }
00083 
00084 
00085 bool
00086 my_i2cWrite (unsigned char data)
00087 {
00088   my_i2cWriteByte (data);
00089   return my_i2cGetAck ();
00090 }
00091 
00092 
00093 unsigned char
00094 my_i2cReadByte ()
00095 {
00096   unsigned char data = 0;
00097 
00098   for (int i = 0x80; i > 0x00; i >>= 1)
00099   {
00100     SCL(0);
00101     SDA(1);
00102     IO_DELAY();
00103 
00104     SCL(1);
00105     IO_DELAY();
00106 
00107     if (sda)
00108     { // turn bit to 1...
00109       data |= i;
00110     }
00111   }
00112   return data;
00113 }
00114 
00115 
00116 unsigned char
00117 my_i2cReadAck ()
00118 {
00119   unsigned char data = my_i2cReadByte ();
00120 
00121   SCL(0);
00122   SDA(0);
00123   IO_DELAY();
00124 
00125   SCL(1);
00126 
00127   // wait till scl is high
00128   IO_DELAY();
00129 
00130   return data;
00131 }
00132 
00133 
00134 unsigned char
00135 my_i2cReadNak ()
00136 {
00137   unsigned char data = my_i2cReadByte ();
00138 
00139   SCL(0);
00140   SDA(1);
00141   IO_DELAY();
00142 
00143   SCL(1);
00144   // wait till scl is high
00145   IO_DELAY();
00146 
00147   return data;
00148 }
00149 
00150 
00151 unsigned char
00152 my_i2cRead (unsigned char ack)
00153 {
00154   if (ack)
00155   {
00156     return my_i2cReadAck ();
00157   }
00158   return my_i2cReadNak ();
00159 }
00160 
00161 
00162 void
00163 my_i2cWriteByte (unsigned char byte)
00164 {
00165   for (int i = 0x80; i > 0x00; i >>= 1)
00166   {
00167     SCL(0);
00168     SDA((byte & i) ? true : false);
00169     IO_DELAY();
00170 
00171     SCL(1);
00172     IO_DELAY();
00173   }
00174 }
00175 
00176 
00177 bool
00178 my_i2cGetAck ()
00179 {
00180   SCL(0);
00181   SDA(1);
00182   IO_DELAY();
00183 
00184   SCL(1);
00185 // wait till clock = 1...
00186   IO_DELAY();
00187 
00188   bool ack = false;
00189   ack = sda;
00190 
00191   return !ack;
00192 }